Fix confusion about the return rowtype of SQL-language procedures.

There is a very ancient hack in check_sql_fn_retval that allows a
single SELECT targetlist entry of composite type to be taken as
supplying all the output columns of a function returning composite.
(This is grotty and fundamentally ambiguous, but it's really hard
to do nested composite-returning functions without it.)

As far as I know, that doesn't cause any problems in ordinary
functions.  It's disastrous for procedures however.  All procedures
that have any output parameters are labeled with prorettype RECORD,
and the CALL code expects it will get back a record with one column
per output parameter, regardless of whether any of those parameters
is composite.  Doing something else leads to an assertion failure
or core dump.

This is simple enough to fix: we just need to not apply that rule
when considering procedures.  However, that requires adding another
argument to check_sql_fn_retval, which at least in principle might be
getting called by external callers.  Therefore, in the back branches
convert check_sql_fn_retval into an ABI-preserving wrapper around a
new function check_sql_fn_retval_ext.

Per report from Yahor Yuzefovich.  This has been broken since we
implemented procedures, so back-patch to all supported branches.

Discussion: https://postgr.es/m/CABz5gWHSjj2df6uG0NRiDhZ_Uz=Y8t0FJP-_SVSsRsnrQT76Gg@mail.gmail.com

src/backend/catalog/pg_proc.c

@@ -945,9 +945,10 @@ fmgr_sql_validator(PG_FUNCTION_ARGS)
 			}
 
 			check_sql_fn_statements(querytree_list);
-			(void) check_sql_fn_retval(funcoid, proc->prorettype,
-									   querytree_list,
-									   NULL, NULL);
+			(void) check_sql_fn_retval_ext(funcoid, proc->prorettype,
+										   proc->prokind,
+										   querytree_list,
+										   NULL, NULL);
 		}
 
 		error_context_stack = sqlerrcontext.previous;

src/backend/executor/functions.c

@@ -744,11 +744,12 @@ init_sql_fcache(FmgrInfo *finfo, Oid collation, bool lazyEvalOK)
 	 * coerce the returned rowtype to the desired form (unless the result type
 	 * is VOID, in which case there's nothing to coerce to).
 	 */
-	fcache->returnsTuple = check_sql_fn_retval(foid,
-											   rettype,
-											   flat_query_list,
-											   NULL,
-											   &fcache->junkFilter);
+	fcache->returnsTuple = check_sql_fn_retval_ext(foid,
+												   rettype,
+												   procedureStruct->prokind,
+												   flat_query_list,
+												   NULL,
+												   &fcache->junkFilter);
 
 	if (fcache->returnsTuple)
 	{
@@ -1590,6 +1591,20 @@ bool
 check_sql_fn_retval(Oid func_id, Oid rettype, List *queryTreeList,
 					bool *modifyTargetList,
 					JunkFilter **junkFilter)
+{
+	/* Wrapper function to preserve ABI compatibility in released branches */
+	return check_sql_fn_retval_ext(func_id, rettype,
+								   PROKIND_FUNCTION,
+								   queryTreeList,
+								   modifyTargetList,
+								   junkFilter);
+}
+
+bool
+check_sql_fn_retval_ext(Oid func_id, Oid rettype, char prokind,
+						List *queryTreeList,
+						bool *modifyTargetList,
+						JunkFilter **junkFilter)
 {
 	Query	   *parse;
 	List	  **tlist_ptr;
@@ -1608,7 +1623,7 @@ check_sql_fn_retval(Oid func_id, Oid rettype, List *queryTreeList,
 
 	/*
 	 * If it's declared to return VOID, we don't care what's in the function.
-	 * (This takes care of the procedure case, as well.)
+	 * (This takes care of procedures with no output parameters, as well.)
 	 */
 	if (rettype == VOIDOID)
 		return false;
@@ -1753,8 +1768,13 @@ check_sql_fn_retval(Oid func_id, Oid rettype, List *queryTreeList,
 		 * will succeed for any composite restype.  For the moment we rely on
 		 * runtime type checking to catch any discrepancy, but it'd be nice to
 		 * do better at parse time.
+		 *
+		 * We must *not* do this for a procedure, however.  Procedures with
+		 * output parameter(s) have rettype RECORD, and the CALL code expects
+		 * to get results corresponding to the list of output parameters, even
+		 * when there's just one parameter that's composite.
 		 */
-		if (tlistlen == 1)
+		if (tlistlen == 1 && prokind != PROKIND_PROCEDURE)
 		{
 			TargetEntry *tle = (TargetEntry *) linitial(tlist);
 

src/backend/optimizer/util/clauses.c

@@ -4624,8 +4624,9 @@ inline_function(Oid funcid, Oid result_type, Oid result_collid,
 	 * Note: we do not try this until we have verified that no rewriting was
 	 * needed; that's probably not important, but let's be careful.
 	 */
-	if (check_sql_fn_retval(funcid, result_type, list_make1(querytree),
-							&modifyTargetList, NULL))
+	if (check_sql_fn_retval_ext(funcid, result_type, funcform->prokind,
+								list_make1(querytree),
+								&modifyTargetList, NULL))
 		goto fail;				/* reject whole-tuple-result cases */
 
 	/* Now we can grab the tlist expression */
@@ -5149,9 +5150,10 @@ inline_set_returning_function(PlannerInfo *root, RangeTblEntry *rte)
 	 * check_sql_fn_retval, we deliberately exclude domains over composite
 	 * here.)
 	 */
-	if (!check_sql_fn_retval(func_oid, fexpr->funcresulttype,
-							 querytree_list,
-							 &modifyTargetList, NULL) &&
+	if (!check_sql_fn_retval_ext(func_oid, fexpr->funcresulttype,
+								 funcform->prokind,
+								 querytree_list,
+								 &modifyTargetList, NULL) &&
 		(get_typtype(fexpr->funcresulttype) == TYPTYPE_COMPOSITE ||
 		 fexpr->funcresulttype == RECORDOID))
 		goto fail;				/* reject not-whole-tuple-result cases */

src/include/executor/functions.h

@@ -36,6 +36,12 @@ extern bool check_sql_fn_retval(Oid func_id, Oid rettype,
 								bool *modifyTargetList,
 								JunkFilter **junkFilter);
 
+extern bool check_sql_fn_retval_ext(Oid func_id, Oid rettype,
+									char prokind,
+									List *queryTreeList,
+									bool *modifyTargetList,
+									JunkFilter **junkFilter);
+
 extern DestReceiver *CreateSQLFunctionDestReceiver(void);
 
 #endif							/* FUNCTIONS_H */

src/test/regress/expected/create_procedure.out

@@ -106,7 +106,19 @@ CALL ptest4a(a, b);  -- error, not supported
 $$;
 ERROR:  calling procedures with output arguments is not supported in SQL functions
 CONTEXT:  SQL function "ptest4b"
-DROP PROCEDURE ptest4a;
+-- we used to get confused by a single output argument that is composite
+CREATE PROCEDURE ptest4c(INOUT comp int8_tbl)
+LANGUAGE SQL
+AS $$
+SELECT ROW(1, 2)::int8_tbl;
+$$;
+CALL ptest4c(NULL);
+ comp  
+-------
+ (1,2)
+(1 row)
+
+DROP PROCEDURE ptest4a, ptest4c;
 -- named and default parameters
 CREATE OR REPLACE PROCEDURE ptest5(a int, b text, c int default 100)
 LANGUAGE SQL

src/test/regress/sql/create_procedure.sql

@@ -68,7 +68,16 @@ AS $$
 CALL ptest4a(a, b);  -- error, not supported
 $$;
 
-DROP PROCEDURE ptest4a;
+-- we used to get confused by a single output argument that is composite
+CREATE PROCEDURE ptest4c(INOUT comp int8_tbl)
+LANGUAGE SQL
+AS $$
+SELECT ROW(1, 2)::int8_tbl;
+$$;
+
+CALL ptest4c(NULL);
+
+DROP PROCEDURE ptest4a, ptest4c;
 
 
 -- named and default parameters